Re: [xsl] XSLT 2.0 courses?

Subject: Re: [xsl] XSLT 2.0 courses?
From: "Imsieke, Gerrit, le-tex gerrit.imsieke@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>
Date: Mon, 21 Sep 2020 11:18:31 -0000
In its original sense, bzw. (beziehungsweise) means 'respectively', but yes, it has assumed the additional meaning of something like 'or', 'or else', or 'or rather'.

'or else' is appropriate for the operator, but it might be a nightmare grammar-wise (XPath grammar, not English grammar).

On 21.09.2020 13:01, Michael Kay mike@xxxxxxxxxxxx wrote:
Perhaps we should call it "bzw" - a German word that is sadly missing from English.


On 21 Sep 2020, at 11:58, Imsieke, Gerrit, le-tex gerrit.imsieke@xxxxxxxxx <mailto:gerrit.imsieke@xxxxxxxxx> <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx <mailto:xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>> wrote:

Thank you, this is convincing.

One might consider naming the 'otherwise' operator 'alternatively', but this is not the hill I'm going to die on.


On 21.09.2020 12:53, Michael Kay mike@xxxxxxxxxxxx <mailto:mike@xxxxxxxxxxxx> wrote:
Well, I thought about using EBV, so it means (if ($a) then $a else $b), but zero is falsey, so you get surprises with, for example
@price * (1 + (@VAT_Rate otherwise 0.2))
which potentially gives the wrong answer if @VAT_Rate is present but zero. And it also gets complicated with atomization: if the attribute is present but set to a zero length string, which way do you go?
Michael Kay
On 21 Sep 2020, at 11:21, Imsieke, Gerrit, le-tex gerrit.imsieke@xxxxxxxxx <mailto:gerrit.imsieke@xxxxxxxxx> <mailto:gerrit.imsieke@xxxxxxxxx <mailto:gerrit.imsieke@xxxxxxxxx>> <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx <mailto:xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> <mailto:xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx <mailto:xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>>> wrote:

If the boolean variable $a is false() instead of an empty sequence,

$a otherwise $b

will return false(). This is the specified behaviour, but I find it a bit counterintuitive. I have a slight preference for the otherwise operator to return $b if $a is false().

Have you thought about defining the otherwise operator as "it returns $a unless it's an empty sequence or a boolean value equal to false(), in which case it returns $b"? I'm not sure which one will seem more natural to most users.


On 21.09.2020 10:46, Michael Kay mike@xxxxxxxxxxxx <mailto:mike@xxxxxxxxxxxx> <mailto:mike@xxxxxxxxxxxx <mailto:mike@xxxxxxxxxxxx>> wrote:
I've been proposing ($a otherwise $b) to meet this requirement: it returns $a unless it's an empty sequence, in which case it returns $b.
For example @price - (@discount otherwise 0)
It's actually implemented in Saxon 10 if you switch syntax extensions on.
Michael Kay
On 21 Sep 2020, at 02:34, Pieter Lamers pieter.lamers@xxxxxxxxxxxx <mailto:pieter.lamers@xxxxxxxxxxxx> <mailto:pieter.lamers@xxxxxxxxxxxx <mailto:pieter.lamers@xxxxxxxxxxxx>> <mailto:pieter.lamers@xxxxxxxxxxxx <mailto:pieter.lamers@xxxxxxxxxxxx> <mailto:pieter.lamers@xxxxxxxxxxxx <mailto:pieter.lamers@xxxxxxxxxxxx>>> <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx <mailto:xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> <mailto:xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx <mailto:xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>> <mailto:xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx <mailto:xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> <mailto:xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx <mailto:xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>>>> wrote:


An avid user of ($a, $b)[1] myself, which winks at TransactSQL ISNULL($a, $b) and MySQL IFNULL($a, $b), I do have to remind myself that $a has to be a single item for the /if/else /shortcut to work.

So, in

let $a := ('one','two','three')
let $b := ('none')

return ($a, $b)[1] will return just the first item in the sequence, 'one', and not 'one','two','three', which might be what you want to achieve in this quasi shorthanded /if/else /construction.

Not that you wouldn't know, Liam, just as a heads up to some others in this audience who might not.


On 19/09/2020 01:54, Liam R. E. Quin liam@xxxxxxxxxxxxxxxx <mailto:liam@xxxxxxxxxxxxxxxx> <mailto:liam@xxxxxxxxxxxxxxxx <mailto:liam@xxxxxxxxxxxxxxxx>> wrote:
On Fri, 2020-09-18 at 19:31 +0000, Wendell Piezwapiez@xxxxxxxxxxxxxxx <mailto:Piezwapiez@xxxxxxxxxxxxxxx> <mailto:Piezwapiez@xxxxxxxxxxxxxxx <mailto:Piezwapiez@xxxxxxxxxxxxxxx>>

In addition to Liam's list I think there are a couple more vital
one needs to get a taste of in XSLT 2.0 or XSLT 3.0, if one has been
subsisting on an XSLT 1.0 diet:

* <xsl:for-each-group> and its uses
* temporary trees -
* regex support in functions and xsl:analyze-string
* tunnel parameters?
Yeah, those are all huge, although i think easier to learn than things
like ($a, 'none')[1], which are startling because XSLT 1 didn't have

For those wondering, ($a, $b, $c, ...)[1] returns the first non-empty
non-false item out of $a, $b and $c, so it's a shortcut for
B B B B <xsl:sequence select="if ($a) then $a else $b" />

On regular expressions - it's huge, but it's also dangerous, as e.g. replace(price div 100, '\.\d*$', '') is not a good way to write math:floor().

An XSLT-3-from-scratch course could easily take a full week and be
woefully incomplete. Or totally overwhelming. Or both.

On the other hand, i try & include "don't be afraid of the specs" in
the courses i teach, and then not cover every detail. So maybe it's


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